Support Go To Definition on properties/items

For properties/items, there isn't a definition per se, but searching
for places where they are written/assigned seems like a reasonable
interpretation that makes F12 more useful.

Partial fix for #163

MonoDevelop.MSBuild.Editor/Navigation/MSBuildNavigationService.cs

@@ -1,6 +1,8 @@
 // Copyright (c) Microsoft. All rights reserved.
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
+#nullable enable annotations
+
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
@@ -109,6 +111,16 @@ public bool Navigate (MSBuildNavigationResult result, ITextBuffer buffer)
 				return true;
 			}
 
+			if (result.Kind == MSBuildReferenceKind.Item) {
+				FindItemWrites (result.Name, buffer).LogTaskExceptionsAndForget (logger);
+				return true;
+			}
+
+			if (result.Kind == MSBuildReferenceKind.Property) {
+				FindPropertyWrites (result.Name, buffer).LogTaskExceptionsAndForget (logger);
+				return true;
+			}
+
 			if (result.Paths != null) {
 				if (result.Paths.Length == 1) {
 					EditorHost.OpenFile (result.Paths[0], 0);
@@ -263,6 +275,46 @@ async Task FindTargetDefinitions (string targetName, ITextBuffer buffer)
 			await searchCtx.OnCompletedAsync ();
 		}
 
+		async Task FindPropertyWrites (string propertyName, ITextBuffer buffer)
+		{
+			var searchCtx = Presenter.StartSearch ($"Property '{propertyName}' writes", propertyName, true);
+
+			try {
+				await FindReferences (
+					searchCtx,
+					(doc, text, logger, reporter) => new MSBuildPropertyReferenceCollector (doc, text, logger, propertyName, reporter),
+					buffer,
+					result => result.Usage switch {
+						ReferenceUsage.Declaration or ReferenceUsage.Write => true,
+						_ => false
+					});
+			} catch (Exception ex) when (!(ex is OperationCanceledException && searchCtx.CancellationToken.IsCancellationRequested)) {
+				var logger = LoggerService.GetLogger<MSBuildReferenceCollector> (buffer);
+				LogErrorFindReferences (logger, ex);
+			}
+			await searchCtx.OnCompletedAsync ();
+		}
+
+		async Task FindItemWrites (string itemName, ITextBuffer buffer)
+		{
+			var searchCtx = Presenter.StartSearch ($"Item '{itemName}' item", itemName, true);
+
+			try {
+				await FindReferences (
+					searchCtx,
+					(doc, text, logger, reporter) => new MSBuildItemReferenceCollector (doc, text, logger, itemName, reporter),
+					buffer,
+					result => result.Usage switch {
+						ReferenceUsage.Declaration or ReferenceUsage.Write => true,
+						_ => false
+					});
+			} catch (Exception ex) when (!(ex is OperationCanceledException && searchCtx.CancellationToken.IsCancellationRequested)) {
+				var logger = LoggerService.GetLogger<MSBuildReferenceCollector> (buffer);
+				LogErrorFindReferences (logger, ex);
+			}
+			await searchCtx.OnCompletedAsync ();
+		}
+
 		delegate MSBuildReferenceCollector ReferenceCollectorFactory (MSBuildDocument doc, ITextSource textSource, ILogger logger, FindReferencesReporter reportResult);
 
 		/// <remarks>
@@ -271,7 +323,8 @@ async Task FindTargetDefinitions (string targetName, ITextBuffer buffer)
 		async Task FindReferences (
 			FindReferencesContext searchCtx,
 			ReferenceCollectorFactory collectorFactory,
-			ITextBuffer buffer)
+			ITextBuffer buffer,
+			Func<FindReferencesResult, bool>? resultFilter = null)
 		{
 			var openDocuments = EditorHost.GetOpenDocuments ();
 
@@ -314,6 +367,10 @@ await ParallelAsync.ForEach (jobs, Environment.ProcessorCount, async (job, token
 
 					void ReportResult (FindReferencesResult result)
 					{
+						if (resultFilter is not null && resultFilter (result) == false) {
+							return;
+						}
+
 						var line = job.TextSource.Snapshot.GetLineFromPosition (result.Offset);
 						var col = result.Offset - line.Start.Position;
 						var lineText = line.GetText ();

MonoDevelop.MSBuild/Language/MSBuildNavigation.cs

@@ -88,6 +88,14 @@ IEnumerable<string> GetAnnotatedPaths ()
 				}
 			}
 
+			if (rr.ReferenceKind == MSBuildReferenceKind.Item) {
+				return new MSBuildNavigationResult (MSBuildReferenceKind.Item, rr.GetItemReference (), rr.ReferenceOffset, rr.ReferenceLength);
+			}
+
+			if (rr.ReferenceKind == MSBuildReferenceKind.Property) {
+				return new MSBuildNavigationResult (MSBuildReferenceKind.Property, rr.GetPropertyReference (), rr.ReferenceOffset, rr.ReferenceLength);
+			}
+
 			if (rr.ReferenceKind == MSBuildReferenceKind.Target) {
 				return new MSBuildNavigationResult (MSBuildReferenceKind.Target, rr.GetTargetReference (), rr.ReferenceOffset, rr.ReferenceLength);
 			}